In the attached I made a sheet called Pop Out Parameters. I made a calc that just grabs the value of the selection parameter, and I used it as a filter so that it only displays anything when the value of the parameter is "Date Range".

I made a wide container on Dashboard 1 that has the sheet, and the two date parameters. I set the date params to fixed width, but not the pop out sheet. And I hid the title of the pop out sheet. Now change the value of Select parameter and see what it does.

On dashboard 2 I repositioned that container so that most of it is off the dashboard. (You can use a negative value for the x- or y-coordinate to push something off the dashboard.) Now when the pop-out sheet shrinks, the two date parameters slide to the left, and the get positioned off the view of the dashboard. Select "Date Range" and the pop-out sheet expands, pushing the parameters onto the dashboard.

This technique is called popping.

PS: on the pop out sheet I added a bogus dimension just so that there is something simple on either rows or columns. If you don't have a dimension on either shelf, even if the sheet goes blank it does not completely disappear on the dashboard. Also I formatted the sheet so it has no lines and so the text is white (so that it doesn't show up on the dashboard when part of it sticks out when it pushes the parameters into view.) You should also disable tooltips on that sheet in case the user ever clicks in that space. I didn't do that here, but you can get that.